In many instances, material in particulate form is dispensed and packaged, as for example, the packaging of pharmaceutical powders, such as penicillin.
A need exists for the rapid dispensing of such materials with high weighing accuracy, for example, within one percent. The close tolerance in the weighing is important in controlling the doses that will subsequently be dispensed to patients.
One method that is now being used for penicillin is to assume that volume is nearly equivalent to a known weight, and on this basis, dispense reproducible volumes of powder. However, this volumetric method does not provide repeatability within one percent. A second method is to use strain gages as a method of measuring force and therefore, weight. Strain gauges are very temperature sensitive and their analog output makes them very sensitive to electronic drift. While the limitations in the above methods can be minimized with engineering effort, a satisfactory solution to the overall problem is not now apparent.
Accordingly, the present invention provides a new and improved method of dispensing and weighing matter in particulate form.